CORRELATION OF RAPID CELL-DEATH WITH METABOLIC CHANGES IN FUNGUS-INFECTED, CULTURED PARSLEY CELLS

To study in detail the hypersensitive reaction, one of the major defen se responses of plants against microbial infection, we used a model sy stem of reduced complexity with cultured parsley (Petroselinum crispum ) cells infected with the phytopathogenic fungus Phytophthora infestan s. Experimental conditions were established to maintain maximal viabil ity of the cultured cells during co-cultivation with fungal germlings, and a large proportion of the infected parsley cells responded to fun gal infection with rapid cell death, thereby exhibiting major features of the hypersensitive reaction in whole-plant-pathogen interactions. Rapid cell death clearly correlated with termination of further growth and development of the fungal pathogen. Thus, the system fulfilled im portant prerequisites for investigating cell-death-related metabolic c hanges in individual infected cells. Using cytochemical methods, we mo nitored the increase of mitochondrial activity in single infected cell s and the intracellular accumulation of reactive oxygen species prior to the occurrence of rapid cell death. We obtained strong correlative evidence for the involvement of these intracellularly accumulating rea ctive oxygen species in membrane damage and in the resulting abrupt co llapse of the cell.